1. Field of the Invention
The invention relates to compatible polymer blends composed of at least two different types of polymer components, whereby the one polymer component Pl is of the poly(methyl)styrene type, while the other polymer component P2 is of methacrylic ester terpolymers.
2. Description of the Background
As a rule, different polymer species are not compatible when mixed or blended, i.e. down to negligible proportions of a component. Different polymer species do not generally form a homogenous phase, which could be characterized by complete miscibility of the components. Certain exceptions to this rule have led to growing interest of those skilled in the art to such homogenous polymer blends, in particular to, theoretical explanations of the phenomena.
Totally compatible polymer blends exhibit complete solubility (miscibility) in all blending ratios. In order to prove miscibility, the glass temperature Tg or the so-called "optical method" (clarity of a film cast from a homogenous solution of a polymer mixture) has been frequently observed. (Cf. Brandrup-Immergut, Polymer Handbook, 2nd ed., III-211-213; Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd ed., Vol. lB, pp. 443-478, J. Wiley & Sons 1982).
The polymers - polystyrene and polymethyl methacrylate (PMMA) - are examples of almost complete incompatibility. (cf. 0. Olabisi, L.M. Robeson, M.T. Shaw, Polymer-Polymer Miscibility, Academic Press, 1979, pg. 4 ff.) However, polystyrene, poly-m-methylstyrene and poly-p-methylstyrene are quite compatible with polycyclohexyl(meth)acrylate (cf. unpublished German Patent Application Nos. P 36 32 369.1 and P 36 38 443.7). Interestingly, no compatibility has been determined for such polystyrenes with polymers composed of other, aliphatic methacrylic esters.
However, compatibility still exists even if the cyclohexyl methacrylate is copolymerized to a certain extent with methyl methacrylate. This finding is interesting primarily from the point of view of commercial application since pure polycyclohexyl methacrylate is extremely brittle. A need therefore continues to exist for improved blends of polystyrene materials with polycyclohexylmethacrylate.